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It was a fellow blogger Sconzani who runs a wonderful blog with the lovely tiltle Earthstar ~ a celebration of nature who got me looking much more closely at the leaves on not only the trees, but most anything else which has leaves.
Leafminers can be from different insect groups. Many species of Lepidoptera (moths), Diptera (trues flies), Coleoptera (beetles) and Symphyta (sawflies), have larvae which mine plants. It is the larvae of these insects which produce these mines within the leaves of plants, feeding on the plants’ tissues as part of their development cycle.
Mines tend to be restricted to a certain range of host plants and so the identification of a miner is facilitated by correctly identifying these plants. The shape of the mines (gallery or blotch) and the patterns of the droppings (frass), besides characteristics of the larvae and pupae, can be diagnostic. Even the location of where the egg is layed on a leaf can be diagnostic and can help to separate similar species.
The Holly Leaf Miner (above image) forms quite a wide gallery on Holly (Ilex), and is only one of two holly leaf miners to be found in the wholes of Europe, and the only one to be found in the UK. The adult female Agromyzid fly Phytomyza ilicis lays its eggs in May or June at the base of the petiole of a young leaf (on the underside). The oviposition scars can be seen on the midrib on the underside of the leaf. The larva initially feeds in the mid-rib, later producing the characteristic irregular upper surface linear-blotch.
The fly Phytoliriomyza melampyga mines the leaves of Impatiens species (Balsams). Here it was found on Himalayan Balsam (Impatiens glandulifera), an invasive plant species here.
The larva of the micro-moth the Apple Leaf-miner (Lyonetia clerkella) feeds on a variety of Rosaceae (rose family) and Betula (birch) trees in small, long and winding leafmines.
The larva of the sawfly Profenusa pygmaea mine the leaves of various species of oak (Quercus) creating a large blister or blotch mine on the upper surface.
So next time you are out in the woods … or even in the park or garden … take a closer look at those leaves and see what squiggly patterns or blotches have been created within them.